Perhaps you have three sons and desperately want a little girl, or maybe you're from a big family of females and wish for your one child to be a boy. Whatever the case, hoping to have a baby of a particular sex is an individual desire.
Google 'how to make a girl/boy baby' and a whole plethora of theories and suggestions come up, but is there any truth to these concepts, or are they just old wives' tales?
"This is an area that has fascinated people over the ages and perhaps has more relevance in the modern age where family size is generally smaller, and so the issue of having children of the sex you desire is more critical," Professor Michael Holland from the University of Queensland told The Huffington Post Australia.
"Though we should start by recognising that any sex selection method that has only two possible outcomes will produce offspring of the desired sex about 50 percent of the time."
A brief history lesson
"The topic of sex selection has a long history, dating at least to the Romans and Ancient Greeks, although I suspect it extended beyond this but unfortunately no written records tell this tale," Holland said.
"The ancient view of women as being a lesser version of men dates to at least Aristotle, and so females were seen as the result of 'incorrect' conception."
Being good observers, the Greeks realised men had two testicles and women two ovaries.
"They theorised that boys resulted from sperm from the right testicle, fertilising ova from the right ovary. Both the Greeks and Romans though the right side of anything was superior to the left, hence the Latin for 'left' - translating to sinister - has entered English to convey these suspicions."
"The ultimate extension of this view came in the 18th century French text The Art Of Boys which recommended actual removal of the left testicle if a son and heir were the desired outcome!" Holland said.
A young Alexander the Great with Aristotle. Alex was probably sick of listening to him bang on about having boys.
If women weren't already discriminated against with regards to this topic, they then had to endure less than desirable practices to ensure a boy.
"In both ancient times and into the Middle Ages a favourite technique which many unfortunate women was the use of animal body parts, nearly always the testes, to help aid in having a boy. Generally these were dried, ground into powder and added to food or drink.
"In these times women were seen as the ones who determined the sex of offspring. The realisation that it is men with the presence of X and Y chromosome bearing sperm who actually determine the sex of the offspring is a relatively recent concept. This lack of understanding meant many of the historical practices were doomed to failure," Holland said.
Fast forward a little into more recent history and the theories continue.
"There is a well known medical text dating from the late 15th century called the Distaff Gospels. This proposed several strategies for having boys, such as having intercourse with the man facing East, avoiding intercourse after food and having intercourse in the morning, as it was thought intercourse at other times produced girls," Holland said.
In the 15th century you had to do it in the morning if you wanted a boy.
"Underlying this was the first appreciation that the timing of intercourse related to the outcome. Later this was linked to the timing of intercourse within the women's period. Indeed this concept of timing forms the basis of the still popular method developed by Landrum Shettles."
"Some theories are relatively harmless, such as the Chinese calendar test, or gender test which first dates from the 13th century. In this test the mother's age at the time of conception and the month in which conception occurred are used to predict the gender," Holland said.
There are some theories which are based loosely on science, the emphasis on "loosely".
"A good example is the Shettles test. This relies on the scientific observation that Y (male) bearing sperm are faster swimmers than X (female) bearing sperm, but do not survive in the female tract as long. Thus intercourse as close to ovulation as possible favours male over female offspring."
Confusing, the other very popular modern day theory, The Whelan Method, completely contradicts this.
"A second example is the basal body temperature method developed by Whelan. This provides the opposite advice -- that intercourse four to six days before ovulation favours male offspring because of basal body temperature effects X sperm survival," Holland said.
"The real truth to me is that sperm selection and survival within the female tract is influenced by many factors, some of which are well understood and some are not. The outcome in terms of gender is a combination of all these factors and simple chance."
The bottom line
While anecdotally many swear by these theories, they really have no significant scientific backing.
"The written historical record dating from the Ancient Greeks and Romans to today indicate our obsession with sex selection and sex determination. These are generally based on folklore, superstition and many are illogical and even silly (though this is not to suggest people who want to know the sex of their baby are silly) and a few can cause injury and affect the health of the baby or mother," Holland said.
"In this case it's interesting to note that in a study where pregnant women who had no idea of the sex of their offspring were asked to nominate the sex they were correct 71 percent of the time so perhaps mum does know best!"
Guessing the sex
Once bub is conceived the theories don't stop. Everyone has their favorite method of guessing the sex of an unborn baby and meany of these are rooted in history, too.
"There are many different ways to determine the gender of an unborn foetus in different cultures. Most have dubious basis in science but many are still repeated in our present culture," Holland says.
- How you walk -- right foot first and you are carrying a boy and left foot first it's a girl
- The key test -- put a key in front of a pregnant woman and if she picks it up by the fat end it's a boy by the slim end it's a girl
- The paternal weight test -- fathers who put on weight during a pregnancy have daughters
- The maternal taste test -- if the mother to be craves sweet foods she is carrying a girls (well we all know girls are sweet, don't we?)
- Wedding ring test -- a gold wedding ring attached to a string and held over the pregnant abdomen will move in circles if it's a boy and back and forth if it's a girl
- How high the pregnancy is being carried -- low carriage it's a boy and higher it's a girl
- Morning sickness test -- the more frequently and more severely you have morning sickness means you are carrying a girl
- Ask mum -- the test is when a pregnant woman asks you what sex you think her child will be you say " delightful boy". If she blushes it's a girl
- There is an interesting historical version of this which involves sprinkling salt of the head of a sleeping pregnant woman and if the first name she says on awakening is male or female you have your answer.